The strike, scheduled to take place between 4pm and 8pm on Wednesday, coincides with with the popular Web Summit conference, attended by an estimated 80,000 people. Uber’s chief product officer, Jeff Holden, gave his keynote speech on Wednesday morning.

The National Association of Alternative Transportation Platform Partners (ANPATT), which represents drivers for ride-hailing apps like Uber and Spanish rival Cabify, confirmed to Business Insider that it had called on drivers to strike to coincide with the summit.

ANPATT spokesman João Pica told Business Insider that drivers were protesting their treatment by Portuguese police.

“We are being targeted by the police,” he told Business Insider. “The law is at the moment in parliament and [because] it has not passed yet the police chase us. We don’t approve.”

ANPATT claimed police had issued the equivalent of €5,000 (£4,422) in tickets during just one day of Web Summit.

It isn’t clear how many drivers are likely to participate in the protest. According to local publication Eco, Uber has 3,000 drivers in Portugal – with the bulk almost certainly located in the country’s capital. One hour into the scheduled strike, Uber’s app still showed driver availability close to Feira Internactional de Lisboa, where Web Summit takes place.

Web Summit and Uber did not respond to a request for comment. However, Web Summit emailed attendees warning them of possible action on Wednesday.

Business Insider understands that Web Summit and Uber are monitoring the situation.

Strikes are nothing new for Uber to deal with, though it’s unusual for the company’s own drivers to strike. The ride-hailing firm is often protested by local taxi drivers who complain Uber drivers are driving down prices unfairly.